In return MSD will make 300,000 doses of the vaccine are available from May 2016 for use in clinical trials or emergencies while its development continues. Submitting an emergency use application to the World Health Organization (WHO), as MSD has done, will allow the vaccine to be used if there is an outbreak before it becomes licensed.

Gavi CEO Dr Seth Berkley said: “The suffering caused by the Ebola crisis was a wake-up call to many in the global health community. New threats require smart solutions and our innovative financing agreement with Merck will ensure that we are ahead of the curve for future Ebola outbreaks.”

Separately, the global shortage of cholera vaccines is set to be eased after the WHO approved a third producer of the vaccine in a move which will double supplies worldwide.

Current supplies of cholera vaccine are outstripped by demand which meant requests from Sudan and Haiti for supplies of the vaccine in case of possible epidemics last year had to be denied.

Now the WHO has approved a third supplier under its pre-qualification programme, which ensures the quality and safety of drugs and bought by countries and international agencies such as UNICEF.

The appointment of a third supplier, South Korean company EuBiologics, is expected to double global supply to 6m doses in 2016 and there is the potential for further increased production in the future.

“This additional capacity will contribute to reversing a vicious cycle of low demand, low production, high price and inequitable distribution,” said the WHO.

There are between 1.4m and 4.3m cases of cholera a year and up to 142,000 deaths. The disease can kill within hours if untreated.

In January the WHO said that a cholera epidemic in Tanzania has infected more than 14,000 people and claimed 222 lives.

Historically there has been a low demand for the cholera vaccine as the disease affected mainly poor communities who were unaware of its existence.

In 2013 the WHO created the world's first stockpile of cholera vaccines, initially pledging to source two million doses - enough to treat one million people - per year.